1. Technical Field
The present invention relates to an optical image capturing lens system. More particularly, the present invention relates to a compact optical image capturing lens system applicable to electronic products.
2. Description of Related Art
In recent years, with the popularity of mobile products with camera functionalities, the demand for miniaturizing an image lens system is increasing. The sensor of a conventional photographing camera is typically a CCD (Charge-Coupled Device) image sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. As advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact image lens system has gradually evolved toward the field of higher megapixels, there is an increasing demand for compact image lens system featuring better image quality.
A conventional compact image lens system in a portable electronic product typically utilizes a three-element lens structure. Such a conventional image lens system has a first lens element with positive refractive power, a second lens element with negative refractive power and a third lens element with positive refractive power. The first, second and third lens elements are arranged in this order from an object-side to an image-side. While the three-element lens structure is compact, it is not able to produce high quality images.
Another conventional compact image lens system provides a four-element lens structure. In the said image lens system, the difference between the minimum effective radius and the maximum effective radius is large, so that the angle of incident light on the image sensor is too large and the sensitivity of the image sensor would be worse. The angles of the incident light on the surfaces of the lens elements are too large which would generate the stray light by the reflection. Moreover, said image lens system includes a small stop which cannot reduce the interference of diffraction and lead to worse image quality. The small stop also cannot raise the incident light, so that the small stop cannot increase the image quality under insufficient lighting condition.
Therefore, a need exists in the art for providing an image lens system for use in a mobile electronic product that has excellent imaging quality without too long total track length, and with small difference between the minimum effective radius and the maximum effective radius and large stop.